High dynamic range (HDR) synthesis is known as a photographing method of expressing a dynamic range wider than a general photographing method. An example of the HDR synthesis method includes a method of pairing two horizontal lines for which an exposure time is different and adding signal charges of pixels for which the exposure time is different for each pair of two horizontal lines.
According to this method, the resolution of an HDR synthesis image in a direction perpendicular to a horizontal line is a half of the number of pixels included in a pixel array of an image sensor. When the number of pixels in the vertical direction of the pixel array is equal to or greater than the double of a target resolution in the vertical direction of the HDR synthesis image, the target resolution can be ensured for the HDR synthesis image. When the number of pixels in the vertical direction of the pixel array is less than the double of the target resolution in the vertical direction of the HDR synthesis image, there is a problem that an image quality may deteriorate due to a decrease in the resolution of the HDR synthesized image. In some case, due to a relation of an optical size of a camera module or the like, it is difficult to set the number of pixels in the vertical direction of the pixel array to be twice the target resolution of the HDR synthesis image.